Have a look at ?par and check out the 'xaxp' parameter par(mfrow=c(1,2)) plot(x[,2] ~ x[,1], xaxp=c(0,100,5)) plot(x[,2] ~ x[,1], xaxp=c(0,100,10), cex.axis=0.5) -- View this message in context: http://n4.nabble.com/Plot-specification-for-grid-of-x-axis-tp1460005p1460083.html Sent from the R help mailing list archive at Nabble.com.